Due to unavoidable room layout, one of my Mordaunt-Short 906 towers was partly obscured by a couch arm, which completely hid the bottom woofer and partly hid the midrange. Sound was definitely compromised because of this, though the speakers sounded good otherwise, with decent bass. They have floor spikes, and were on a carpeted floor. In an attempt to remedy this I bought a couple of one foot square concrete patio stones and placed them under the speakers, keeping the spikes. Sound clarity improved, but now there is less bass. I think the firm connection with the floor has been lost. The speakers have balast chambers for sand, which I have not used. Would this help? If not, are there any other things I could try to restore the bass?